In a side impact collision, where a vehicle is hit from the side by another vehicle, the impact is typically taken by the front and rear doors and the body structure surrounding the doors. An arm rest structure on the inside of the vehicle doors is primarily provided as a convenience feature to support one arm of each of the occupants. Typically, the armrest structure is padded on the outside with foam for comfort and has interior structure such as one or more brackets to provide substantial vertical stiffness to support service and abuse loads (such as in the extreme case of someone standing on the armrest to access the roof). The arm rest must also have enough lateral stiffness to enable opening and closing of the door using a door handle incorporated in the arm rest. The armrest should also have sufficient fatigue strength to withstand the repeated door openings and closings over the life of the vehicle. To satisfy these requirements, the armrest ends up being a very stiff structure that does not crush easily so that forcible contact with an occupant's abdomen will result in internal injuries to the occupant in the event of a side impact crash.
Such deformable armrests have heretofore been proposed, as for example in U.S. Pat. Nos. 6,893,077 and 5,951,094.
To cushion the pelvis during such a side impact crash, a foam block is typically placed between the door trim panel and the door inner panel. However, foam suffers from several disadvantages such as a “stack-up” load increase after about 50% to 60% of foam compression due to foam cell wall flattening. Typically there also is degradation of foam material properties over time and at high temperature (e.g., foam can become quite soft in compression at high temperatures).
It is an object of the present invention to provide a vehicle armrest which is capable of supporting substantial vertical loads while being crushable on side impact to effectively protect an occupant from injury by contact with the armrest.
It is a further object of the present invention to provide a side impact pelvic cushion which is not subject to age or temperature degradation and is effective through widely varying range of loadings.